Effects of Diltiazem on Myogenic Tone in Pressurized Brain Arteries from Spontaneously Hypertensive Rats

1986 ◽  
pp. 107-113 ◽  
Author(s):  
G. Osol ◽  
R. Osol ◽  
W. Halpern
Keyword(s):  
Spontaneously Hypertensive Rats ◽  
Myogenic Tone ◽  
Hypertensive Rats ◽  
Spontaneously Hypertensive ◽  
Brain Arteries

Myogenic tone in mesenteric arteries from spontaneously hypertensive rats

1996 ◽  
Vol 270 (1) ◽  
pp. H1-H6 ◽  
Author(s):  
A. S. Izzard ◽  
S. J. Bund ◽  
A. M. Heagerty
Keyword(s):  
Spontaneously Hypertensive Rats ◽  
Mesenteric Arteries ◽  
Myogenic Tone ◽  
Hypertensive Rats ◽  
Tension Development ◽  
Spontaneously Hypertensive ◽  
Wide Pressure Range ◽  
Wistar Kyoto ◽  
Wide Pressure

To investigate myogenic tone during the developmental and established phases of hypertension, segments of distal (6th order) mesenteric arteries from spontaneously hypertensive rats (SHR) at 5 and 20 wk were isolated and pressurized in vitro and compared with vessels from age-matched Wistar-Kyoto (WKY) control animals. At 5 wk, tone was significantly enhanced in the SHR. At 20 wk tone was no longer significantly increased over a wide pressure range, although arteries from the SHR were able to maintain diameter at all pressures studied, whereas vessels from the WKY exhibited forced distension at 180 and 200 mmHg. From the relative slope of the pressure-diameter relationship (myogenic index), no increase in peak myogenic responsiveness was observed in arteries from the SHR at either time point. Passive lumen diameters were significantly decreased in arteries from SHR at both time points. From the total and passive midwall circumference-tension relationships, total tension was observed at a reduced midwall circumference in the SHR, but increased absolute levels of total tension were not observed. The normalized midwall circumference-tension relationships in the two strains revealed increased total tension due to active tension development at a reduced normalized circumference at 5 wk in the SHR. At 20 wk the normalized midwall circumference-tension relationships in the two strains were identical. These results demonstrate that myogenic tone in mesenteric arteries is enhanced during the development of hypertension but not when it is established, except at high intraluminal pressures.

Enhanced Stretch-Induced Myogenic Tone in the Basilar Artery of Spontaneously Hypertensive Rats

2007 ◽  
Vol 44 (3) ◽  
pp. 182-191 ◽  
Author(s):  
Duck-Sun Ahn ◽  
Soo-Kyoung Choi ◽  
Young-Hwan Kim ◽  
Young-Eun Cho ◽  
Heung Mook Shin ◽  
...  
Keyword(s):  
Basilar Artery ◽  
Spontaneously Hypertensive Rats ◽  
Myogenic Tone ◽  
Hypertensive Rats ◽  
Spontaneously Hypertensive

Myogenic Tone in Coronary Arteries from Spontaneously Hypertensive Rats

1997 ◽  
Vol 34 (2) ◽  
pp. 109-116 ◽  
Author(s):  
Susana R. Garcia ◽  
Ashley S. Izzard ◽  
Anthony M. Heagerty ◽  
Stuart J. Bund
Keyword(s):  
Coronary Arteries ◽  
Spontaneously Hypertensive Rats ◽  
Myogenic Tone ◽  
Hypertensive Rats ◽  
Spontaneously Hypertensive

Influence of Mode of Contraction on the Mechanism of Acetylcholine-Mediated Relaxation of Coronary Arteries from Normotensive and Spontaneously Hypertensive Rats

1998 ◽  
Vol 94 (3) ◽  
pp. 231-238 ◽  
Author(s):  
Stuart J. Bund
Keyword(s):  
Coronary Arteries ◽  
Spontaneously Hypertensive Rats ◽  
Statistical Significance ◽  
Myogenic Tone ◽  
Internal Diameter ◽  
Flow Conditions ◽  
Hypertensive Rats ◽  
Spontaneously Hypertensive ◽  
Wistar Kyoto ◽  
Endothelium Dependent Relaxation

1. Endothelium-dependent acetylcholine-mediated relaxations of small coronary arteries (∼200 μm internal diameter) from 20 weeks old spontaneously hypertensive rats (SHR) and normotensive Wistar—Kyoto (WKY) controls were compared under pressurized no-flow conditions after the development of myogenic tone or constriction with the thromboxane A2 mimetic U46619. 2. Relaxations of WKY and SHR arteries following development of myogenic tone did not differ and were not significantly influenced by indomethacin alone (10 μmol/l) or in combination with Nω-nitro-l-arginine (l-NNA, 0.1 mmol/l). Maximum relaxations were significantly attenuated by 30 mmol/l K+ in the SHR, from 85 ± 7% (n = 11) to 20 ± 8% (n = 8), P < 0.001, and in the WKY from 86 ± 5% (n = 9) to 39 ± 14% (n = 8), P < 0.01. 3. Relaxations following constriction with U46619 were also similar in both rat strains. Maximum relaxations were 50 ± 11% (n = 8) in SHR and 60 ± 7% (n = 6) in WKY. Indomethacin did not influence these relaxations. The combination of indomethacin and l-NNA attenuated relaxations in WKY (P < 0.01), but in the SHR the attenuation did not achieve statistical significance (P = 0.07) compared with controls; the maximum responses were reduced to 25 ± 7% (n = 8) and 14 ± 11% (n = 6) in the SHR and WKY respectively, but only in the WKY was this reduction significant (P < 0.05). 4. These data demonstrate that, under control conditions, SHR and WKY coronary arteries relax equally effectively, regardless of mode of contraction, and also that the mechanism of acetylcholine-mediated relaxation differs according to the mode of contraction. Acetylcholine relaxes myogenic tone by a K+-sensitive mechanism in both WKY and SHR, consistent with a role for endothelium-derived hyperpolarizing factor; NO contributes substantially to the relaxation of U46619-induced tone by acetylcholine in the WKY, but to a diminished extent in the SHR. 5. These data indicate that the choice of vasoconstrictor agent is of critical concern when assessing mechanisms of endothelium-dependent relaxation and abnormalities thereof in hypertension.

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